Remove logfile if it's empty before exiting

cmd/after-lock/after-lock.go

@@ -25,7 +25,7 @@ func main() {
 	defer handleErrors()
 	f := initLogging()
 	if f != nil {
-		defer f.Close()
+		defer teardownLogging(f)
 	}
 
 	lock := grabExclusiveProcessLock()

cmd/after-lock/logging.go

@@ -18,3 +18,20 @@ func initLogging() *os.File {
 	log.SetOutput(f)
 	return f
 }
+
+func teardownLogging(f *os.File) {
+	fi, err := f.Stat()
+	if err != nil {
+			panic(err)
+	}
+	if fi.Size() == 0 {
+			err = os.Remove(f.Name())
+			if err != nil {
+					panic(err)
+			}
+	}
+	err = f.Close()
+	if err != nil {
+			panic(err)
+	}
+}